High dose Si- and Mg-implantation in CaN: Electrical and structural analysis

The implantation of Si-donors and Mg-acceptors in GaN was studied for doses from 1 x 10(14) to 1 x 10(16) cm(-2) and annealing at 1100 degrees C. The transport and luminescence properties were compared to Ar-implanted samples at the same doses. For a Si dose of 1 x 10(16) cm(-2) a sheet electron density of 5 x 10(15) cm(-2) was measured after annealing. Since a same dose Ar-implant resulted in only a sheet electron density of 3.3 x 10(13) cm(-2), the flee electron density in the Si-sample is not attributable to implant damage but is the result of electrically active Si-donors. For a Mg dose of 5 x 10(15) cm(-2) the sheet carrier concentration is only 8 x 10(11) cm(-2) which suggests, even when accounting for the ionization energy of Mg in GaN of similar to 170 meV, that no significant Mg-activation has occurred or that it is compensated by the implantation induced damage. Channeling Rutherford backscattering and cross-sectional electron microscopy demonstrates that at high doses (6 x 10(15) cm(-2)) even annealing at 1100 degrees C, as required to activate implanted dopants, does not significantly reduce the implantation induced disorder. Therefore, at least for Si-donors, the complete removal of implant damage is not required to achieve electrically active implanted dopants in GaN.